Features
Accepts inputs from 15V to 450V
Output currents up to 3.0mA continuous, 30mA peak
Supply current typICally 50μA
Line regulation typically 0.1mV/V
Output can be trimmed from 8.0V to 12V
Output current can be increased to 150mA with
external FET
Applications
Off-line SMPS startup circuits (pulse loads)
Low power off-line regulators
Regulators for noisy inputs
The Supertex LR645 is a high input voltage, low output
current linear regulator. It has a 3-terminal fi xed output voltage
version available in TO-92, TO-220 and SOT-89 packages,
as well as an adjustable voltage version available in an 8-
lead SOIC package. The 3-terminal version functions like any
other low voltage 3-terminal regulator except it allows the use
of much higher input voltages. When used in a SMPS startup
circuit, it eliminates the need for large power resistors. In
this application, current is drawn from the high voltage line
only during start-up. Only leakage current fl ows after start-up,
thereby reducing the continuous power dissipation to a few
milliwatts.
The adjustable voltage version allows trimming of the output
voltage from 8.0V to 12V. This version can also be connected
to an external depletion mode MOSFET for increased output
current. When used in conjunction with Supertex depletion
mode MOSFET DN2540N5, an output current of up to 150mA
is achieved.